1. Field of the Invention
The present invention relates to a pipeline computer, and more particularly, relates to a control method for a scoreboard in a pipeline computer.
2. Description of the Related Art
In a pipeline computer, a scoreboard (or SCG) is known as a method for managing and controlling the mutual dependency of operands which are used in a calculation. As one example, the scoreboard is used for an interference detection in the general registers as explained in detail below.
That is, a scoreboard storage unit is provided for indicating an in use state or a not used state of each general register. When executing an instruction which writes data into a general register (i.e., write instruction), a bit in the scoreboard corresponding to the number of the register is set to the set state to indicate that a write operation is being executed. Further, when an instruction writes a result of a calculation into a general register, a bit in the scoreboard corresponding to the number of the register, is set to the reset state to indicate that the write operation has been completed.
In this case, to confirm whether or not the rewriting of the bit has been executed by a preceding instruction by a source operand, an instruction which follows the preceding instruction (hereinafter referred to as the "following instruction") reads the bit corresponding to the register number which indicates the source operand. If the bit is set, that indicates that the rewriting based on the preceding instruction is not completed, and the following instruction waits for the start of a calculation.
If the bit on the scoreboard is reset, since the preceding instruction does not rewrite the source operand, the following instruction can start the calculation.